Composite materials provide high electrical resistance in comparison with metallic materials. The latter have traditionally been used in the field of aeronautics for the manufacture of structures intended for fuel storage given their mechanical characteristics in relation to the weight of these materials.
The high electrical resistance inherent to composite materials causes a highly relevant induction effect in internal fuel tank systems. Said effect induces internal electrical currents that may give way to catastrophic failures or phenomena for the overall structural integrity.
The phenomena related to moderate or severe electrical discharges occurring in the case of lightening striking which must be avoided in a structure made of a material with low electrical conductivity so as to assure its structural integrity/malfunction of any of the critical electrical equipment/electric arcs inside the tank:
Hot spots: the high density of current in certain specific locations of the structure such as joints or intersection elements may generate high temperature spots. If this temperature exceeds 200° C. (point of auto-ignition of the fuel considered by FAA/JAA authorities), the fuel may reach its ignition point.
Electric arcs (sparking): the flow of current through materials with different resistances and in geometrically spaced locations may cause discharges in the form of an electric arc (potential difference) and causing the ignition of the fuel/inflammable liquid contained in the structure.
Electrical equipment malfunction: the electrical discharges caused by lightening striking give way to high levels of current circulating through the outer structure and may therefore introduce electric current through the internal systems either by shunting or induction. These effects are capable of causing critical equipment malfunction, generating a catastrophic failure.
Patent application PCT/ES05/070133 of Airbus describes a method for protecting the assembly of metallic devices assembled inside a fuel tank, completely or partially manufactured with composite materials, for protection against electrical discharges, in which insulating inserts are required in the installation lines for the fuel, ventilation, etc., such that they are subdivided into parts insulated from one another.
This invention relates to an insulating insert of the type that can be used both in locations with little free space and in areas of insulating floating elements with greater length.